Sprint Doesn't Believe I Canceled My Account

Chase thought he had ditched Sprint for Verizon, but Sprint is still billing him and said it has no record of him canceling the account. He doesn’t want to pay his bill and feels stuck to the company he left. He writes:

I just got off the phone with Sprint customer service and am less than impressed. On December 8th, I had my number ported over when I canceled my Sprint account and transferred to Verizon. Verizon reps assured me that the transfer would be handled on their end, but just to be sure, I called Sprint that day to make sure my phone had been canceled. The representative I spoke with assured me that since I just paid my current balance (that day, December 8th), my account would be canceled and I would receive no further bills.

Today, I found a bill in the mail with full monthly charges. I called Sprint and they told me that they “saw I had ported out” but the line was still active, and Verizon must not have submitted the cancellation properly. I told them I had spoken with a Sprint representative and had been told the cancellation went through. The rep remarked that there was no record of the call, and there was nothing he could do. I asked for someone higher and he connected me to David, who identified himself as an escalation manager. I told him my story and he said “there is a stamp which would go on your account if you had called. You did not call. The charges are valid.” Whenever I assured him that I had spoken with a representative, he would interrupt me and say “No you didn’t. No you didn’t.” It was childish and infuriating.

David also assured me that his decision was final, and I when I told him I’d be taking it up the chain, he said “There is no one at Sprint who can override my decision.” Help me prove him wrong, Consumerist! I left a voicemail with the executive customer service number you have posted, but they aren’t open on the weekends. If they can’t help me, do I have any other recourse?